Vacuum switch with liquid filled bellows operation



Sept. 30, 1969 S. BEDDOE Filed Sept. 30, 1966 2 Sheets-Sneet 1 I m g: 15 -q Faun 27 19 S 20 Q 16 19 E ii 25 III/77;

\ FIG.1

FIGS

' APPLICANT Stanley Beddoe BY ATTORNEYS Sept. 30, 1969 s. BEDDOE 3,470,341

VACUUM SWITCH WITH LIQUID FILLED BELLOWS OPERATION Filed Sept. 50, 1966 2 Sheets-Sheet 2 United States Patent Claims priority, application Gr/eat Britain, Sept. 30, 1965, i if 41,637 Int. Cl. H01h9/30, 33/ 66- us. Cl. 200-144 4 Claims ABsrnAcronrnn DISCLOSURE A vacuum switch having a pair of contacts in an evacuated casing; a bellows interconnects one of the contacts and the casing, and forms part of the wall of the evacuated casing, and of a closed chamber outside the evacuated casing. Insulating'liquid is supplied to .the closed chamber, both to move the contact between open" and closed positions, and to damp oscillations in the bellows and contact system, thus preventing contact bounce. The liquid may be transformer oil.

This invention relates to electric switchgear.

According to this invention, a vacuum switch has a movable contact sealed to the casing by bellows or the like, and the movable contact is moved between the open and closed positions by means of a fluid pressure applied to the bellows or the like.

Embodiments of this invention will now be described by way of example with reference to the accompanying drawings, of which:

FIG. 1 is a section through a first embodiment of vacuum switch in accordance with the invention,

FIG. 2 is a view similar to FIG. 1 of a second embodiment,

FIG. 3 shows an arrangement including a number of vacuum switches of the first embodiment arranged in series, and,

FIG. 4 shows an arrangement including a number of vacuum switches of the second embodiment arranged in series.

Referring to FIG. 1, the vacuum switch includes a casing, including a cylindrical insulator 11 bonded to end members 12, 13 one at each end, the end members being sealed in turn to end plates 14, 15. It will be understood that the interior of the casing operates at a high vacuum.

One end plate 14 has a fixed electrode means or contact 16 secured to it, and is provided with a terminal 17 for connection in an external circuit.

The movable contact 18 is in the centre of the other end plate 15, and is connected to it by a flexible metal bellows 19 extending between the end plate and a flange 27 on the contact stem. The bellows 19, together with part of the end plate 15, the flange 27, and an end housing 20, defines a closed chamber 21 which is supplied with an insulating liquid through a pipe 22 of insulating material. The liquid, which may for example be transformer oil, serves two purposes; first, increase of the pressure of the liquid causes closing of the contacts, and decrease of the pressure allows them to open; and secondly the liquid provides damping of oscillations which have been found to occur in the bellows and which limit their useful life.

Opening of the contacts, on decrease of the liquid pressure, is ensured by a tension spring 23 between the interior of the hollow movable contact 18 and the end housing 20. A sliding connection is provided between the movable contact 18 and the end housing by resilient 3,470,341 Patented Sept. 30, 1969 fingers 24, which serve both as a guide for movement of the contact and to convey the current to the terminal 25 on the end'housing.

The usual shields '26 are provided to protect the insulator11 from'metal deposition due to arcing between the contacts 16,18. '-In operation, an increase of pressure is produced in closed chamber 21, by suitable means (not shown), for example by a valve controlling a supply of the liquid under pressure to pipe 22. This increase causes the bellows 19- to extend, so that the movable contact 18 is brought into engagement with fixed contact 16.

' Referring now to FIG. 2, there is shown a vacuum switch which'in many respects is similar to that of FIG.

two breaks in series. Instead of a single end plate 15 associated with the movable contact 18 and connected to a terminal 25, the two endplates 15A" of a pair of identical vacuum switch units for engagement or mutual cooperative relationship are connected together by a cylindrical electrical conductor 28 and the two movable contacts 18A are electrically connected back-to-back. The movable contacts 18A are connected to the endplates by respective bellows 19A, and the bellows together with endplates 15A and conductor 28 define a closed chamber 21A. This is supplied with liquid, in a similar manner to that described with reference to FIG. 1, through a pipe 22A of insulat ing material and the opening force is provided by a tension spring 23A connected between the hollow movable contacts 18A. The movable contacts are connected by a bridging finger-type connection 24A, located symmetrically by inter-connection with the conductor 28. In an alternative a pair of tension springs may be provided between a central member, carried for example by the condoctor 28, and the respective movable contacts 18A.

The operation is similar to that of the switch of FIG. 1, that is, on application of pressure to chamber 21A through pipe 22A the movable contacts 18A make contact with the fixed contacts 16, and on decrease of the pressure the spring 23A causes both pairs of contacts to break.

It will be understood that the contacts 16, 18, 18A may be of any known or convenient form, and in particular the contacts 16 need not be rigidly fixed, and are preferably resiliently mounted, although referred to as the fixed contacts, as is well in the art.

Referring to FIG. 3, a number of vacuum switches as described with reference to FIG. 1 are shown connected in series, the terminal 17 of one being connected, as shown, to the terminal 25 of the next. The pipes 22 of each switch are connected to a common supply line 29 for simultaneous operation of the switches.

In FIG. 4, two vacuum switches as described with reference to FIG. 2, each switch having two units, are shown connected in series, one terminal 17 of each switch being connected by a conductor 30 to the other switch, and the other terminals forming the terminals for connection in an external circuit. The pipes 22A are connected to a common supply line 31.

Instead of the bellows 19, 19A shown, there may be provided suitable equivalent constructions, for example built-up constructions incorporating flexible metal bellows or diaphragms.

I claim:

1. A vacuum switch having two breaks in series, comprising a first evacuated casing; a second evacuated casing; a first pair of contacts relatively movable into and out of engagement, within said first evacuated casing, said first pair of contacts including a first movable contact which is movable relative to said first evacuated casing; first bellows means connecting said first movable contact and. saidfirstevacuated casing; asecond pair -oi 3. A vacuum'switch as claimedin-ciaiml, comprising contacts relatively movable into and out of engagement within said second evacuated casing, said second pair of contacts including a;-second movable -contactwhich is movable relative-to said second evacuated casing; second bellows means connecting said second movablescoiitact andsaid second evacuated casing; means'electrically interconnecting said first mov'ab le contact and said second .A movable contact; means including said firstbellows means and said second bellows means' and defining a closed chamber; and means to supply. an insulating liquid to said closed chamber, whereby variation of the p resure of said insulating liquid causes movement ofthe pressure of-said U ;-first and second pairs of' contacts into and out ofi-engage ment. v 1 H n v I 2. A vacuum switch as claimed in claim-.1, v said evacuated casings comprising an end plate having a central aperture; said billows means beingsealedto said end plate around sai central aperture and ,to. said contacts; said contacts comprising a stem; afixed electrically-conducting member in which said stem is slidableg'. and terminal means electrically connected to. said fixed electricallyconducting member. 4 i

also end housing means secured to said end plate and to said fixed electrically-conducting member; said end plate, said bellows means, and said end housing means each defining tpar t of sthe -b oundj ofsaid closed chamber.

4L A" vacuum switch a s. H ed in claim 3, comprising also resilient c uri7ent-lc rvi'ng finger-' means secured to a and ho s ;1 .e 1, ;and ir e y gagi g; s

stem.

FoREIGN TATENT-S 3 

